This invention relates to the assembly of wall or roofing ceiling panels or concrete form assemblies. The high cost of labor in the building trades has placed a premium on the portability prefabrication and ease of assembly of buildings. Preparation of forms in the construction of concrete structures adds significantly to casts. Numerous patents have been issued relating to prefabricated construction units which employ joint structures which receive and hold panels. An example of one such structure is found in the patent to Shimano, No. U.S. Pat. No. 3,738,083. Others employ dovetailing corner assemblies but require separate fasteners to hold the construction together, such as that disclosed in U.S. Pat. No. 3,585,768 issued to Klein. None of prior art show, however, units which require no nails or outside fasteners and which by the method of construction creates tension in the wall panels which is then transmitted back to the joint structure itself causing it to be closed even more effectively.